With the prevalence of polyethylene/aluminum/polyethylene pipes, more and more research has been done on pipe coupling joint. German Patent DE 199856999A1 disclosed a pipe coupling joint, wherein, the pressure sleeve is fixed to the coupling fitting by a ring-shaped accessory. The end of the inner wall of the pressure sleeve is located at the shoulder section of the coupling fitting, thereby the pressure sleeve can be maintained precisely coaxial with the coupling fitting for a long term. However, the pressure sleeve, which is usually made of metal such as steel and copper, of the joint contacts to the coupling fitting directly, resulting electrochemical corrosion between different metals. Also, a utility model ZL 01274991 granted to this applicant in year 2002 disclosed a coupling joint, said joint contains technical features including a check ring; whereas the configuration of that check ring can not ensure good coaxiality and fixity between the pressure sleeve and the check ring, consequently, the pressure sleeve and check ring are easily disengaged during assembling, resulting hardship and inconvenience during installing.